By analysing the characteristics of the communication channel in a bidirectional digital wireless endoscopy system, the authors propose an efficient automatic repeat query (ARQ) scheme, with a dynamically adaptive block size, a high data rate and an ultra-short communication distance. Two new strategies for adaptive block-size decision are also proposed. The optimum block-size formula for the wireless endoscopy system is given and analysed in detail. This ARQ scheme ensures not only the image's communication quality at a high data rate (2 Mbit/s) but also the optimum communication-power efficiency in the capsule